Most plans now offer two boxes for your contributions, and people agonize over them. The same funds sit in both. The only difference is timing. Traditional dollars go in before tax, cut your taxable income this year, and get taxed as ordinary income when you pull them out. Roth dollars go in after tax, cut nothing this year, and come out tax free in retirement as long as you're past 59½ and the account is at least five years old.

So the question is about tax rates. If your rate today is higher than the rate you'll pay in retirement, traditional wins, because you skip the tax in the expensive year and pay it in the cheap one. If your rate today is lower than it'll be later, Roth wins, for the same reason in reverse. You can't know your retirement rate today. But you can make a reasonable guess from where you are in your career.

Oregon changes the math a little. Most working Oregonians land in the state's 8.75% bracket, and the state taxes 401(k) and IRA withdrawals the same way it taxes wages. Put $10,000 into the traditional side while you're in the 22% federal bracket and that's roughly $3,000 you don't send to Salem and Washington, D.C. this year. Retire in Oregon and you'll pay the state's share when the money comes out. Retire across the river in Washington, where there's no income tax, and the state piece disappears. That's a real difference, and it argues for traditional if a move is a live possibility. I'm a broker, not a CPA, so run the specifics past whoever does your taxes.

Roth dollars are bigger dollars. A $500,000 Roth balance is $500,000 you can spend. A $500,000 traditional balance is that number minus whatever the tax rate is in the year you take it. So two people with identical statements can be in very different positions, and a plan built only on the traditional balance will overstate what you have.

Three details shifted recently. Employer matching money can now go into the Roth side if your plan allows it, though the match is taxable in the year it lands. Roth 401(k) accounts no longer force required minimum distributions. And the annual contribution limit is shared across both boxes, so splitting doesn't let you put in more.

The homework is short: find your marginal bracket on last year's return, decide whether you expect to be above it or below it after you stop working, and put this year's contributions in the box that matches. If you can't decide, split it, and revisit the split every time your income changes.